The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Colorful Cocoa

On a pleasant spring day in Meerbusch, Germany, while in my garden enjoying the midday Sun I noticed these colorful bubbles on the surface of a cup of hot cocoa I was sipping. If the film that forms a bubble is sufficiently thin, diffraction of sunlight (interference) will cause iridescentcolors to appear. The pastel colors that result are due to variations in the thickness of the bubble’s film and to the angle of the observer’s line of sight. A drop of oil or gasoline in a water puddle produces a similar effect. The presence of lipids or oils in the cocoa likely contributes very little to these colorful patterns. Photo taken on April 28, 2013.